Carbs 1
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Questions and Answers

What is the main function of carbohydrates in living organisms?

  • Structural components of cell walls
  • Main energy source (correct)
  • Production of hormones
  • Synthesis of nucleic acids

    • How are carbohydrates classified based on the number of carbon atoms?

  • By the type of carbonyl group they contain
  • By the number of hydrogen atoms they contain
  • By the number of carbon atoms they have (correct)
  • By their function in the body

    • Which organic molecules are the most abundant in nature?

  • Nucleic acids
  • Lipids
  • Proteins
  • Carbohydrates (correct)

    • What is the storage form of energy in animals?

    <p>Glycogen</p> Signup and view all the answers

    Why are carbohydrates important in cell communication?

    <p>Forming glycoproteins</p> Signup and view all the answers

    What is the defining characteristic of isomers?

    <p>They have the same chemical formula but different structures</p> Signup and view all the answers

    Which of the following is an example of an isomer of glucose (C6H12O6)?

    <p>Fructose</p> Signup and view all the answers

    What is the distinguishing feature between alpha and beta isomers?

    <p>The position change of the carbon that carries the aldehyde/keto group</p> Signup and view all the answers

    Which of the following statements about enantiomers is correct?

    <p>They are mirror images of each other</p> Signup and view all the answers

    What is the characteristic that distinguishes D-isomers from L-isomers?

    <p>The position of the hydroxyl group on the asymmetric carbon farthest from the carbonyl group</p> Signup and view all the answers

    What type of bond links monosaccharides together to form disaccharides, oligosaccharides, and polysaccharides?

    <p>Glycosidic bond</p> Signup and view all the answers

    Which of the following is not a type of disaccharide mentioned in the text?

    <p>Galactose</p> Signup and view all the answers

    What type of bond is formed when carbohydrates are attached to non-carbohydrates?

    <p>Glycosidic bond</p> Signup and view all the answers

    Which of the following is not a type of glycoside mentioned in the text?

    <p>Carbs + purine and pyrimidine Nucleic bases</p> Signup and view all the answers

    What type of bond connects the polysaccharide to the protein backbone in mucin?

    <p>O-glycosidic bond</p> Signup and view all the answers

    What is the purpose of digestion according to the text?

    <p>To break down complex nutrients into simple molecules</p> Signup and view all the answers

    Which enzyme is responsible for initiating carbohydrate digestion in the mouth?

    <p>Salivary alpha-amylase (ptyalin)</p> Signup and view all the answers

    Which of the following is NOT a final product of carbohydrate digestion?

    <p>Lactose</p> Signup and view all the answers

    Which cells are responsible for absorbing the monosaccharides produced during carbohydrate digestion?

    <p>Enterocytes</p> Signup and view all the answers

    Which of the following dietary polysaccharides can be digested by most mammals?

    <p>Starch</p> Signup and view all the answers

    Where does the final digestion and absorption of carbohydrates primarily occur?

    <p>Duodenum and upper jejunum</p> Signup and view all the answers

    Which organisms have the necessary enzymes to digest cellulose?

    <p>Ruminants and other herbivores</p> Signup and view all the answers

    Which transporter is responsible for the absorption of monosaccharides in the small intestine?

    <p>Both SGLT1 and GLUT5</p> Signup and view all the answers

    Which of the following is NOT a major dietary polysaccharide?

    <p>Fructose</p> Signup and view all the answers

    What is the primary cause of the symptoms associated with abnormal degradation of disaccharides?

    <p>All of the above</p> Signup and view all the answers

    Which enzyme is responsible for the digestion of lactose?

    <p>Lactase</p> Signup and view all the answers

    Which of the following is NOT a potential reason for abnormal degradation of disaccharides?

    <p>Excessive exercise</p> Signup and view all the answers

    What is the name of the product formed when monosaccharides are joined together?

    <p>Disaccharides</p> Signup and view all the answers

    Which of the following is NOT a common monosaccharide found in nature?

    <p>Glucosamine</p> Signup and view all the answers

    Where do the monosaccharides produced during carbohydrate digestion get absorbed?

    <p>Small intestine</p> Signup and view all the answers

    Which of the following is NOT a type of polysaccharide?

    <p>Lactose</p> Signup and view all the answers

    What is the main function of glucosamine in the body?

    <p>Structural component of cell walls</p> Signup and view all the answers

    Which enzyme is responsible for the digestion of starch into maltose?

    <p>Amylase</p> Signup and view all the answers

    What is the primary role of digestion in relation to nutrients?

    <p>Breaking down complex nutrients into simple molecules</p> Signup and view all the answers

    What is a characteristic of glucosamine in the context of carbohydrates?

    <p>An aminosugar commonly found in polysaccharides like cartilage and chitin</p> Signup and view all the answers

    What is the primary purpose of the absorption process in relation to nutrients?

    <p>Transporting simple molecules across the intestinal epithelium</p> Signup and view all the answers

    Which of the following is a branched polysaccharide?

    <p>Glycogen</p> Signup and view all the answers

    What is the distinguishing characteristic of monosaccharides?

    <p>They are composed of a single sugar unit</p> Signup and view all the answers

    Which of the following statements about the digestion and absorption processes is true?

    <p>Digestion is fruitless if the digested nutrients cannot be absorbed</p> Signup and view all the answers

    Which of the following is NOT a final product of carbohydrate digestion?

    <p>Sucrose</p> Signup and view all the answers

    Which process helps break down carbohydrates before digestion?

    <p>Mastication</p> Signup and view all the answers

    Which of the following statements about the digestion of carbohydrates is correct?

    <p>Salivary amylase initiates the digestion of carbohydrates in the mouth.</p> Signup and view all the answers

    Which of the following is a major dietary polysaccharide?

    <p>Starch</p> Signup and view all the answers

    Which enzyme is responsible for the digestion of lactose, a disaccharide?

    <p>Lactase</p> Signup and view all the answers

    Which of the following is a monosaccharide?

    <p>Glucose</p> Signup and view all the answers

    Study Notes

    Carbohydrates

    • Carbohydrates (CH2O)n are the most abundant organic molecules in nature, serving as the main energy source for most animals, storage form of energy (in animals = glycogen), cell membrane components (glycoproteins – cell communication), and structural components (cell walls of plants, bacteria, fungi, algae; exoskeleton of insects).

    Carbohydrate Classification

    • Carbohydrates can be classified based on the number of carbon atoms (C).
    • They can also be classified depending on the type of carbonyl group they contain (Aldo- or Keto-).

    Carbohydrate Isomers

    • Isomers have the same chemical formula but differ in structure or spatial arrangement of atoms.
    • Examples of isomers include fructose, glucose, mannose, and galactose (C6H12O6).
    • Alpha- and beta-isomers differ in the position of the carbon that carries the aldehyde/keto group.

    Carbohydrate Enantiomers

    • Enantiomers are special types of isomers that are mirror images of each other.
    • Enantiomers are assigned as D- or L-sugars, with most sugars found in nature being D-isomers.
    • D-isomers have the –OH group on the asymmetric carbon farthest from the carbonyl group (CHO) on the right, while in L-isomers, it is on the left.
    • Most enzymes responsible for carbohydrate degradation are specific for either D- or L-isomers.
    • Isomerases are enzymes capable of interconverting D- and L-isomers.

    Monosaccharide Joining

    • Monosaccharides can be joined to form disaccharides, oligosaccharides, and polysaccharides.
    • The bonds that link sugars are glycosidic bonds.
    • Disaccharides are formed by 2 monosaccharides, oligosaccharides by 3-10 monosaccharides, and polysaccharides by more than 10 monosaccharides (up to hundreds!).
    • Important disaccharides include LACTOSE (galactose + glucose), SUCROSE (glucose + fructose), and MALTOSE (glucose + glucose).
    • Important polysaccharides include Branched Glycogen (animal), Starch (plant amylose, amylopectin), and Cellulose.

    Carbohydrates Linked to Non-Carbohydrates

    • Carbohydrates can be attached to non-carbohydrates via glycosidic bonds, forming glycosides.
    • Examples of glycosides include carbohydrates linked to:
      • Purine and pyrimidine → Nucleic bases
      • Aromatic rings → Bilirubin and steroids
      • Proteins → Glycoproteins/proteoglycans
      • Lipids → Glycolipids
    • Mucin is a glycoprotein with an O-glycosidic bond between a polysaccharide and a protein backbone.

    Digestion and Absorption

    • Digestion is the process of breaking down complex nutrients into simple molecules.
    • Absorption is the process of transporting these simple molecules across the intestinal epithelium.
    • Absorption cannot occur if food is not digested, and digestion is fruitless if the digested nutrients cannot be absorbed.

    Dietary Carbohydrate Digestion

    • In most omnivores, carbohydrate digestion begins in the mouth with the enzyme salivary alpha-amylase (ptyalin).
    • Carbohydrate digestion happens mainly in the small intestine, where pancreatic and enterocyte hydrolases (glycosidases) break glycosidic bonds.
    • The final products of carbohydrate digestion are monosaccharides: glucose, fructose, and galactose.
    • Monosaccharides are then absorbed by enterocytes (epithelial cells lining the inner surface of the small and large intestines).

    Main Dietary Polysaccharides

    • Main dietary polysaccharides include starch (plant) and glycogen (animal).
    • Mastication helps break down material, but mammals generally do not have the enzymes necessary to break down cellulose β (1→4) glycosidic bonds.
    • Ruminants and other herbivores have bacteria in their digestive tracts that produce enzymes to digest cellulose.

    Final Digestive Processes and Absorption

    • Final digestive processes and absorption occur at the mucosal lining in the duodenum and upper jejunum.
    • Absorption of the monosaccharide products of carbohydrate digestion occurs by enterocytes.
    • GLUT is a glucose transporter, and SGLT-1 is a sodium (Na+)-dependent glucose cotransporter.

    Major Dietary Carbohydrates

    • Major dietary carbohydrates include starch, glycogen, sucrose (saccharose), and lactose.
    • Salivary amylase starts digestion, and further digestion is achieved by pancreatic enzymes in the lumen of the small intestine.
    • Digestion is finished by enzymes synthesized by the intestinal mucosa, including maltase, isomaltase, lactase, and sucrase.
    • Absorption of carbohydrates (monosaccharides) takes place in the duodenum and upper jejunum by Na+-dependent transport mechanisms (SGLT1) and facilitated transport (GLUT5 and GLUT2).

    Abnormal Degradation of Disaccharides

    • Abnormal degradation of disaccharides can lead to passage of disaccharides into the large intestine, increasing osmotic activity, and bacterial fermentation, resulting in abdominal cramps, diarrhea, and flatulence.
    • Reasons for abnormal degradation include genetic defects, intestinal diseases, malnutrition, pharmaceuticals/drugs that injure the mucosa, lactose intolerance, and age-related reductions in enzyme activities.

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    Carbohydrates 1 VP 2024 PDF

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    Explore the functions and classification of carbohydrates, the most abundant organic molecules in nature. Learn about how carbohydrates serve as the main energy source for animals, storage form of energy, cell membrane components, and structural components in various organisms.

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